Method of making breathable receptacles

ABSTRACT

Disposable receptacles for storing articles in sterile condition and having breather means integral with the walls thereof, as well as apparatus and methods for making such receptacles and the materials therefor, are disclosed. The receptacles are fabricated of a laminate comprising a layer of breathable barrier material such as paper and a layer of thermoplastic, polymeric material such as polyethylene. 
     The breather means may be made by heat sealing the thermoplastic layers of a pair of laminated sheets together at small, selected areas and then separating the sheets causing localized delamination of the layers and the formation of ruptured, blister-like projections in the thermoplastic layers at the heat seal positions.

RELATED APPLICATIONS

This application is a continuation-in-part of abandoned application Ser.No. 55,160 filed July 6, 1979 and entitled "Method of Making BreathableReceptacles", which application was a division of abandoned applicationSer. No. 955,221 filed Oct. 27, 1978 and entitled "SterilizableReceptacles And Methods And Apparatus Relating Thereto".

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of manufacturing disposable,breathable receptacles for storing articles in sterile condition.

2. Description of the Prior Art

Currently, receptacles for sterile packaging of articles, and primarilythose used for medical applications, fall principally within threegeneral categories: pouches with one side made of polyethylene-coatedpaper or of polyethylene film and the other side consisting of abreathable material such as paper or "Tyvek" (a spun polyolefin of thedu Pont Company); pouches or bags having an all-paper constructionutilizing adhesive bonds with the entire surface area of the receptacleserving as the breathing membrane; and pouches or bags with walls madesubstantially entirely of a material, typically polyethylene orpolypropylene, which is impermeable to both microorganisms andsterilizing vapor and having a breathable strip or patch covering a slitor port in the wall.

Receptacles in current use often have limited shelf lives due todeterioration of the membrane material as a result of changes in ambienttemperature and humidity which cause flexing, distortion and sometimespinholding of the membrane material. This is particularly true ofreceptacles whose breathing membrane constitutes a large portion of theoverall area of the receptacle such as those in which the membrane formsan entire wall, or both walls, of the receptacle. Stresses applied tothe membrane walls of such receptacles can be transferred to avulnerable spot accelerating the formation of pinholes or otherwiseweakening the structure sufficiently to eventually create a breakthrough which microorganisms can enter. Another disadvantage of suchreceptacles is that the stored article is directly exposed to largeareas of the fibrous membrane with the possibility of dislodging fibersthrough abrasion or other physical contact.

Moreover, receptacles that are fabricated of two materials areexpensive. The breathable membrane, if paper, must be surgical grade andis significantly more expensive than ordinary paper while "Tyvek" isseveral times the price of paper membrane material. Some suchreceptacles have small windows or ports covered by a patch ofvapor-permeable material. The manufacture of such receptacles requiresexact registration between the port, patch and the mechanism that sealsthe patch to the receptacle thereby necessitating the use of additionalapparatus which substantially increases the cost of the final product.

SUMMARY OF THE INVENTION

Receptacles made in accordance with the present invention solve theabove-described problems by utilizing readily available, low costpre-laminated material such as polyethylene-coated paper. In accordancewith one specific form of the receptacle, there is provided a pair ofopposed walls joined about a portion of their peripheries. At least oneof the walls is a laminate including an outer layer of a material suchas paper which is impermeable to microorganisms but highly permeable tosterilizing vapor, and an inner layer of a polymeric material such aspolyethylene. At least a portion of the laminated wall has breathers forthe introduction and removal of sterilizing vapor, the breatherscomprising ruptured portions of the inner layer. The ruptures in thedelaminated portion of the inner layer at each breather position aresubstantially smaller in area than the corresponding delaminated portionof the outer layer. Such a receptacle is exceptionally strong because ofthe reinforcing provided by the layer of polymeric material. The storedproduct is in contact only with that layer and hence completelyprotected by it. The area of individual ruptures is so small thatvirtually no paper is exposed and contact between the paper and theproduct is thereby effectively precluded.

By incorporating the breathing area directly into the wall of thereceptacle, that is, by making the breathing area an integral part ofthe wall structure, dual material construction such as required in someprior art receptacles is eliminated. The speed of manufacture maytherefore be increased since heat sealable layers are bonded to eachother through the paper substrate allowing an increase in sealertemperatures (which are not critical) with a concomitant decrease indwell time. Moreover, the relatively small size of the ruptures in theinner layer provides an additional barrier to any microorganisms thatmight penetrate the breathing areas of the outer layer. Sterilizingvapor, however, easily passes through the small ruptures.

In accordance with the invention, the fabrication of the receptacles, orof breathable laminate usable for such receptacles, is carried out in aunique and highly efficient manner which takes advantage of the factthat the strength of a heat seal bond between the thermoplastic layersof confronting or superimposed sheets of laminate is initially greaterthan the delamination resistance of the laminate. Generally, inaccordance with one example of the method, the walls are heat sealedtogether at small, selected areas and then separated causing localizeddelamination of the layers and the formation of ruptured, blisterlikeprojections in the thermoplastic layer of one or both walls at thelocation of each of the small heat seals. Only a relatively small numberof these ruptures are necessary to provide adequate breathing tofacilitate the sterilization of the contents of the final package by avapor sterilization process.

DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the detaileddescription of the preferred embodiment, below, taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a perspective view of a sterilizable receptacle made inaccordance with the invention;

FIG. 2 is an enlarged cross-section view of a portion of the receptacleof FIG. 1 as seen along 2--2;

FIG. 3 shows a portion of the inner layer of the laminated wall of thereceptacle as seen along 3--3 in FIG. 2;

FIGS. 4 and 5 are side elevation views, in section, of portions oflaminates and apparatus to illustrate certain of the steps in thefabrication of receptacles such as shown in FIGS. 1-3;

FIG. 6 is a somewhat schematic, perspective view of an apparatus formaking receptacles of the type shown in FIGS. 1-3;

FIG. 7 is a side elevation view, partly in crosssection, of a portion ofthe apparatus of FIG. 6 as seen along 7--7;

FIG. 8 is a perspective view showing the details of certain of theelements of the apparatus of FIG. 6;

FIG. 9 is a bottom view of a portion of one of the heat sealers utilizedin the apparatus of FIG. 6;

FIG. 10 shows, in somewhat schematic form, a side elevation view of anapparatus for making a breathable laminate; and

FIGS. 11 and 12 are end elevation views of portions of the apparatus ofFIG. 10 as seen along 11--11 and 12--12 in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

At the outset, it is to be noted that in the accompanying drawings thethicknesses of the laminates and layers comprising the laminates haveall been greatly exaggerated in order to clearly show theirinterrelationships. Further, certain of the views are somewhat schematicor idealized in order to facilitate description of the invention and toavoid confusion. It will also be evident that a great many combinationsof materials (both opaque and transparent), overall package dimensions,material properties, specific package configurations, and so forth, fallwithin the purview of the claimed invention. Only relatively fewspecific examples are shown and discussed herein and these should not beconstrued as exhaustive.

The term "sterilizing vapor" used herein is intended to include vaporssuch as ethylene oxide, steam, or the like, that are passed into theinterior of a sealed package through a breathable membrane or the likeand withdrawn, typically under partial vacuum, to effect sterilizationof the contents of the package.

FIGS. 1-3 show a disposable, breathable receptacle for receivingarticles to be stored in sterile condition. The receptacle takes theform of a bag 10 made from a heat sealable, pre-laminated sheet or stockcomprising an outer layer 12 of paper, "Tyvek", or the like, and athermoplastic, polymeric film forming an inner layer 14 bonded to theouter layer 12. The layer 12 is highly permeable to sterilizing vaporbut impermeable to microorganisms so as to define, in the final package,an effective barrier to the entry of contaminating agents. By way ofspecific example, the laminate can be polyethylene-coated Kraft paperwhich is commonly available at exceedingly low cost and which provides astrong, protective envelope for the article(s) to be stored.

The laminated sheet has longitudinal edge margins 16 and 18 and isfolded along parallel, longitudinal fold lines 20 so as to bring themargins 16 and 18 into overlapping relationship. These margins arejoined along the entire length of the bag by a longitudinal heat seal 22thereby forming the laminated sheet into a flat tubular structure havingopposed faces or walls 24 and 26. Transverse edges 28 and 30 define theends of the bag. One of the ends is sealed by a transverse heat seal 32while the other end has an opening 34 for receiving the article(s) to bestored.

It will be evident to those skilled in the art that in the alternative,separate, laminated sheets may be superimposed to define the walls 24and 26 and joined by heat sealing or other bonding along theirperipheries save for an opening for inserting the article to bepackaged. Such a construction is known in the art as a pouch andconstitutes another form that the receptacle of the present inventionmay take.

In the specific embodiment of the receptacle depicted in FIGS. 1-3, thelaminated wall has two arrays 36 of small breathers 38 formed by amethod which will be presently described. The breathers 38 allowsterilizing vapor to be introduced into and withdrawn from the interiorof the final, sealed package to effect sterilization of the contents inaccordance with well known techniques.

As shown in FIG. 1, the arrays 36 are generally circular with one arrayon each side of the longitudinal center line of the bag 10, but it willbe obvious that virtually any configuration can be used and thatbreathers can be distributed across the entire area of one wall or bothwalls. It is advantageous, however, to confine the breathers torelatively small regions of the bag wall so as not to adversely affectthe strength of the bag and to avoid any possible contact between theenclosed article and the layer 12 which, as stated, is typically afibrous material such as paper.

The breathers 38 are defined by discrete portions of the wall where theouter and inner layers 12 and 14, respectively, are delaminated orseparated. Each delaminated portion 39 of the outer layer 12 comprisesan individual breathing area in the outer layer. Each delaminatedportion 40 of the inner layer 14 includes vapor-permeable ruptures 42substantially smaller in area than the corresponding breathing area 39in the outer layer. The relatively small size of the ruptures 42provides an additional barrier to any microorganisms that mightpenetrate the breathing areas 39 of the outer layer.

Contact between the enclosed article and the layer 12 is avoided byvirtue of the small size of the ruptures 42. In the particular form ofthe receptacle under consideration, further protection against contactbetween the contents of the package and the paper layer is afforded bypositioning the arrays 36 away from the central portion of the bagwithin which portion the article tends to settle during storage. Forexample, the arrays 36 in the embodiment of FIG. 1 are located adjacentthe opening 34.

Turning now also to FIGS. 4 and 5, a method of making the breathers 38in accordance with the invention will now be described. Although thedescription is in the context of a bag such as that shown in FIGS. 1-3,the method will be applicable generally to other receptacleconstructions and to the production of breathable laminates per se fromlaminated stock for use in medical packaging or the like. Following theformation of the laminated sheet into a tubular structure by theapplication of the longitudinal heat seal 22 to join the margins, a heatsealer 48 having, for example, a circular working surface consisting ofa gridwork of individual, square faces 50, is applied to the outer,paper layer 12 of one of the walls 24. In accordance with one practicalexample of the invention, the heat seal faces 50 of the heat sealer 48are 1/16" squares with 1/16" spacings between rows and columns of sealfaces. A backing plate 52 positioned opposite the heat sealer 48supports the bag during this sealing operation. The heat sealer 48effects a series of individual seals 54 between the confrontingthermoplastic layers of the walls 24 and 26. The impressions made by theheat sealer 48 remain on the outside surface of the paper as shown inFIG. 1.

Following this operation and preferably while the individual seals arestill at somewhat elevated temperature, a separator plate 56 having atapered or rounded leading edge 58 is inserted into the tubular bagstructure to separate the walls 24 and 26. By performing this step whilethe seals are still hot, the bond between the outer and inner layers 12and 14 is slightly weakened and helps prevent fibers from beingdislodged from the outer layer 12. Since at the outset the strength ofthe individual heat seals is greater than the delamination resistance ofthe laminate, a small portion of the polymeric layer under and abouteach seal is pulled away from the paper as the separator plate advancesresulting in localized delamination of the inner and outer layers.Further advancement of the plate 56 apparently causes the portions ofthe inner layer about the individual seals to stretch and ruptureresulting in a structural configuration appearing somewhat like thatshown in FIG. 3. It will be understood that FIG. 3 is highly idealized;in practice, when viewed under magnification, the shapes of theblister-like, ruptured projections appear quite irregular.

The resulting bag is strong, provides excellent protection andincorporates, in an exceedingly simple and low cost manner, an integralbreather.

FIGS. 6-9 show in somewhat schematic form an apparatus for making thebags of FIGS. 1-3 on a commercial scale. Following manufacture of thebag on the apparatus of FIGS. 6-9, an article is inserted and the openend sealed with a transverse heat seal. As is well known in the art, thebag may be formed, filled and sealed on a single machine combining theseoperations. In either case, the resulting package is then exposed to asterilizing vapor which permeates through the breathers and sterilizesthe article and the interior surfaces of the package. After purging ofthe sterilizing vapor, the package is stored until the enclosed articleis ready for use. Opening of the bag can be facilitated in any of anumber of ways well known in the art.

The bags are formed from a continuous web 70 of the earlier describedlaminated stock drawn from a supply roll 72 and maintained under therequired tension. The web 70 is advanced step-by-step a distance of onebag length by an intermittently rotatable feed drum 74 actuated by asuitable drive unit (not shown). As it advances, the web 70 is folded inwell known fashion about a plate mandrel 75 by the action of forming andfolding members collectively represented by the angularly orientedroller elements 76. The web 70 is thus formed into a continuous sleeveor tube 78 with the margins 70a and 70b being disposed in overlappingrelation. The tube 78 thus envelopes the plate mandrel 75 which isinterposed between an upper wall 80 and a lower wall 82 of the flattenedtube 78.

During each dwell between successive advancements of the tube 78, alongitudinal, vertically movable heat sealer 84 disposed above the platemandrel 75 and having a single, central heat seal bar 86 is operated tojoin the confronting margins of the web 70 by means of a heat seal 88.

Following application of the longitudinal heat seal 88, small individualheat seals joining the heat sealable layers of the walls 80 and 82 areformed at a heat seal station 89 just downstream of the longitudinalheat sealer 84. The seals are applied by a heat sealer 90 having a pairof spaced, circular sealer members 92 each consisting of an array ofprojecting sealing elements 94 arranged in a grid pattern. Each sealingelement 94 has a square face 96 approximately 1/16" on a side and spacedapart a distance of 1/16" both longitudinally and transversely asalready described. Again, the size, shape and spacing of the sealingelements 94 and their faces 96 as well as the overall configuration,size and placement of the breather arrays are not limited to thatdescribed which is to be construed as exemplary only.

The sealer members 92, one of which is disposed on one side of thelongitudinal center line of the tube 78 and the other of which islocated on the other side of the tube center line, join the superimposedwalls of the tube 78 with arrays of individual heat seals as alreadydescribed in connection with FIGS. 1-5.

Disposed inside the tube 78 just downstream of the sealing station 89 isa V-shaped plate 100 the function of which is to separate the walls 80and 82 to produce an array of breathers in the manner described above inconnection with FIGS. 4 and 5. The separator plate 100, which has arounded or gradually tapered leading edge 102, is held in place againstthe movement of the advancing tube by a rod or wire 104 connecting thetip of the plate 100 with the center of the trailing edge of the platemandrel 75 (FIG. 8). The separator plate 100 may assume shapes otherthan that specifically shown and alternative means will suggestthemselves to those skilled in the art for separating the portions ofthe walls 80 and 82 that have been sealed by the heat sealer 89. Forexample, the walls can also be separated by a surge of pressurized airintroduced into the tube via a conduit using a mechanism, for example,generally along the lines as disclosed in U.S. Pat. No. 3,837,972.

Following separation of the walls 80 and 82 by the plate 100, the tubeis drawn about the feed drum 74. At this station along the path of thetube a transverse seal 106 joining the walls of the tube is applied by atransverse heat sealer 108 which is pressed down on the tube during eachdwell period. The position of the transverse seal 106 relative to thebreather arrays is controlled by a three-roller compensator mechanism110 the operation and structure of which is well known in the art. Fromthe feed drum 74 the tube is advanced to a cutting station (not shown)where the tube is separated into individual bags. It will be appreciatedthat bag fabrication as well as filling and sealing of the resultingpackage may be performed on a single "form and fill" machine.

FIG. 10 shows an apparatus for the continuous, high speed fabrication ofwebs of breathable laminate for use in making sterilizable receptaclesof the type already discussed as well as breathable, removable coversfor trays such as that disclosed in U.S. Pat. No. 4,022,324. Suchbreathable laminate may also be employed for making vapor-permeable,peelable strip material for medical packages such as disclosed in U.S.Pat. No. 3,472,369.

The apparatus of FIG. 10 includes a pair of supply rolls 120 and 122 forsupplying webs 124 and 126 each of which is a laminated structure ofpaper 124a, 126a and heat sealable material 124b, 126b, or theequivalent as already described. The webs 124 and 126 are drawn off therolls 120 and 122 by a first drive roller 128. The webs converge andtheir heat sealable layers 124b and 126b are brought into contact aboutan idler roller 130 disposed between the supply rolls and the driveroller 128.

A first rotary heat sealer 132 adjacent the drive roller 128 and biasedinto contact with the paper layer 126a applies a first set of small,individual heat seals bonding the heat sealable layers 124b and 126b.The first rotary heat sealer 132, which has a plurality of projectingheat seal elements 134, may extend across the entire width of the webs.Alternatively, the length of the heat sealer 132 and its position alongthe width of the webs may be chosen so as to apply the small, individualheat seals along any selected path along the length of the webs. Forexample, as shown in FIG. 11, the roller 132 may have a length somewhatless than one-half the overall width of the superimposed webs 124, 126and be positioned to one side of the center line 136 of the webs.

In the example of FIG. 11, the heat seal elements 134 projecting fromthe rotary heat sealer 132 are arranged in parallel rows to provide agrid-like pattern of individual seals similar to the pattern previouslydescribed. Alternatively, the elements 134 can be grouped in virtuallyany desired formation.

The webs 124 and 126 are drawn off the first drive roller 128 by asecond drive roller 138 about which the heat sealable layers of the websare again brought into intimate contact. Positioned between the firstand second drive rollers 128 and 138 is a stationary separator plate 140of metal or plastic, such as "Teflon", inserted between the webs 124 and126 for separating the webs in the manner already described with theresult that discrete breathers are produced in heat seal layers 124b and126b at the positions of the heat seals formed by the rotary sealer 132.Preferably, the distance along the web between the heat sealer 132 andthe plate 140 is sufficiently short so that the heat seals made by thesealer 132 are still at elevated temperature when they arrive at theleading edge of the plate 140.

The second drive roller 138 has coacting therewith a second rotary heatsealer 142 which applies a second set of small, individual heat sealsthrough the paper layer 124a and which may be identical to the firstheat sealer 132. Thus, the sealer 142 may extend across the entire widthof the webs or only across a portion of the width as shown in theexample of FIG. 12. In the event the paths of the heat seals produced bythe rotary sealers 132 and 142 overlap (such as would be the case, forexample, if they extended the entire width of the webs), the drive unitsof the sealers 132 and 142, which drive units have been omitted from thedrawing for the sake of clarity, should be synchronized so that thesecond set of seals are staggered, that is, out of registration, withrespect to the first set of seals. As in the case of the first sealer132, the individual sealing elements 144 of the second sealer may bearranged in virtually any pattern.

Downstream of the second roller 138 is a second, stationary separatorplate 146 whose function and structure is the same as the first plate140. The webs proceed about an idler roller 148 and from there they areseparately wound into rolls 150 and 152. The breathable webs thusproduced are ready to be used in the manufacture of bags, pouches, traylids, or the like, or other products which may employ such laminates.Instead of being wound into supply rolls 150, 152, the webs may proceeddirectly to bag or pouch-making mchines or to "form and fill" packagingmachines.

Although there have been described a number of alternative forms andmodifications of the various aspects of the invention, it will beappreciated that the invention encompasses all modifications andvariations falling within the scope of the appended claims.

What is claimed is:
 1. A method of making a breathable receptacle forstoring an article in sterile condition, the receptacle beingconstructed of a laminate comprising a layer of paper or the likeimpermeable to microorganisms but highly permeable to sterilizing vaporand a layer of thermpolastic, polymeric material, the strength of a heatseal bond between layers of the polymeric material being initiallygreater than the delamination resistance of the laminate, the methodincluding the steps of:superimposing first and second sheets of saidlaminate with the polymeric layers in confronting relation; heat sealingthe polymeric layers of said sheets together at a plurality of smallareas; separating the sheets thereby rupturing the polymeric layer of atleast one of the sheets at the positions of the small areas; and joiningthe sheets together to define the receptacle.
 2. A method of making abreathable bag for storing an article in sterile condition, the bagbeing constructed from a laminated web having longitudinal edge marginsand comprising a layer of paper or the like impermeable tomicroorganisms but highly permeable to sterilizing vapor and a layer ofthermoplastic, polymeric material, the strength of a heat seal bondbetween layers of the polymeric material being initially greater thanthe delamination resistance of the web, the method including the stepsof:folding the web along longitudinal fold lines to bring thelongitudinal edge margins of the web into overlapping relationship; heatsealing the overlapping edge margins together with a continuous,longitudinal heat seal to form a flattened tube having confrontingwalls, the layer of paper, or the like, constituting the outer layer ofthe tube; heat sealing together the polymeric layers of the confrontingwalls at a plurality of small areas; separating the walls therebyrupturing the polymeric layer of at least one of the walls at thepositions of the small, heat sealed areas; and applying a transverseheat seal across the width of the flattened tube to form a sealed bagend.
 3. A method of making a breathable laminate from laminated stockincluding a layer of paper or the like and a layer of heat sealablematerial, said method comprising the steps of:bringing the heat sealablelayer of a sheet of said stock into contact with a heat sealablesurface; bonding said heat sealable layer of said sheet to said heatsealable surface with a plurality of small, individual heat sealsapplied through said paper layer, the strength of said bonds beinginitially greater than the delamination resistance of said layers; andseparating said sheet from said heat sealable surface thereby rupturingthe heat sealable layer at the locations of the various individual heatseals.
 4. A method of making a breathable laminate from laminated stockcomprising a layer of paper or the like and a layer of heat sealablematerial, the strength of a heat seal bond joining layers of said heatsealable material being initially greater than the delaminationresistance of the laminate, said method comprising the stepsof:superimposing first and second sheets of said stock with the layersof heat sealable material in contact; bonding the heat sealable layersto each other with a plurality of small, individual heat seals appliedthrough the paper layer of at least one of the sheets; and separatingthe sheets thereby rupturing the heat sealable layer of at least one ofthe sheets at the positions of the individual heat seals.
 5. A method ofcontinuously making a breathable laminate from laminated stockcomprising a layer of paper or the like and a layer of heat sealablematerial, said method comprising the steps of:superimposing first andsecond, continuous webs of said stock with the layers of heat sealablematerial of said webs in contact; bonding the heat sealable layers toeach other with a first set of small, individual heat seals appliedthrough the paper layer of the first web; separating the webs therebyrupturing the heat sealable layer of at least one of the webs at thepositions of the individual heat seals of the first set of seals; againsuperimposing said webs, bringing the layers of heat sealable materialof said webs into contact; bonding the heat sealable layers to eachother with a second set of small, individual heat seals applied throughthe paper layer of the second web, said second set of heat seals beingstaggered with respect to the first set of heat seals; and separatingthe webs thereby rupturing the heat sealable layer of at least one ofthe webs at the positions of the individual heat seals of the second setof seals.
 6. A method of continuously making a breathable laminate fromlaminated stock comprising a layer of paper and a layer of heat sealablematerial, the strength of a heat seal bond joining layers of said heatsealable material being initially greater than the delaminationresistance of the laminate, said method comprising the stepsof:superimposing first and second, continuous webs of said stock withthe layers of heat sealable material of said webs in contact and theedges of said webs in registration, said superimposed webs having acommon, longitudinal center line; bonding the heat sealable layers toeach other with a first set of small, individual heat seals appliedthrough the paper layer of the first web along a path on one side of thecenter line; separating the webs thereby rupturing the heat sealablelayer of at least one of the webs at the positions of the individualheat seals of the first set of seals; again superimposing said webs,bringing the layers of heat sealable material of said webs into contact;bonding the heat sealable layers to each other with a second set ofsmall, individual heat seals applied through the paper layer of thesecond web along a path on the other side of the center line; andseparating the webs thereby rupturing the heat sealable layer of atleast one of the webs at the positions of the individual heat seals ofthe second set of seals.